Inhibition of influenza m2 proton channel

ABSTRACT

Provided are compounds that are capable of modulating the activity of the influenza A virus via interaction with the M2 transmembrane protein. Also provided are methods for treating an influenza A-affected disease state or infection comprising administering a composition comprising one or more compounds that have been identified as being capable of interaction with the M2 protein.

The present application claims priority to U.S. Provisional App. No. 61/097,474, filed Sep. 16, 2008, the entire contents of which are hereby incorporated in their entirety.

STATEMENT OF GOVERNMENT RIGHTS

Research leading to the disclosed invention was funded in part by the U.S. National Institutes of Health, grant numbers GM56423 (William F. DeGrado) and AI 74571 (William F. DeGrado). Accordingly, the United States Government may have certain rights in the invention described herein.

TECHNICAL FIELD

The present invention pertains to, among other things, compounds and methods for modulating the activity of the influenza virus.

BACKGROUND

The M2 protein is found in the viral envelope of influenza A virus and functions as a highly selective, pH-regulated proton channel important for the life cycle of the virus. Unlike neuraminidase inhibitors, rimantadine and amantadine are anti-viral agents capable of blocking the tetrameric M2 channel. In 2006, the CDC issued an alert instructing clinicians to avoid using M2 ion-channel inhibitors during influenza season due to the extraordinarily high frequency of amantadine resistance in influenza A isolates associated with a single point mutation in the M2 protein, S31N (Hayden F. G., Antiviral Resistance in Influenza Viruses—Implications for Management and Pandemic Response, N Enj J Med, 2006, 354; 8). The drug-binding site is lined by residues that are mutated in amantadine-resistant viruses. Grambas, S., Bennett, M S. & Hay, A. J. Influence of amantadine resistance mutations on the pH regulatory function of the M2 protein of influenza A viruses. Virology 191, 541-549 (1992); Bright, R. A., Shay, D. K., Shu, B., Cox, N. J. & Klimov, A. I. Adamantane resistance among influenza A viruses isolated early during the 2005-2006 influenza season in the United States. J. Am. Med. Assoc. 295, 891-894 (2006). Recently, it has been reported that resistance to rimantadine and amantadine in humans, birds and pigs has reached more than 90%, casting into doubt the continued ability of these drugs alone to satisfy the need for treatment of influenza (Deyde, V. M. et al. Surveillance of resistance to adamantanes among influenza A(H3N2) and A(H1N1) viruses isolated worldwide. J. Infect. Dis. 196, 249-257 (2007)).

Previous studies have suggested that BL-1743 (3-(4,5-Dihydro-1H-imidazol-2-yl)-3-aza-spiro[5.5]undecane) interacts differently with the M2 proton channel as compared with amantadine, but have found that the majority of isolated influenza viruses that are amantadine-resistant are also resistant to BL-1743. Tu Q, et al., Characterization of inhibition of M2 ion channel activity by BL-1743, an inhibitor of influenza A virus, J. Virol. 1996 July; 70(7):4246-52. For example, Tu Q, et al. found that mutations known to confer amantadine resistance at M2 residues 27, 30, 31, and 34, all within the M2 transmembrane domain, also induce “complete” resistance to BL-1743. Id. The publication by Tu Q, et al. concluded that “the overlapping spectra of amantadine and BL-1743 resistance mutations and the higher apparent K_(i) . . . do not indicate that BL-1743 should replace the use of amantadine (or rimantadine) for the prophylaxis or treatment of influenza virus infections in humans.” Id. See also Kurtz, et al., Growth impairment resulting from expression of influenza virus M2 protein in Saccharomyces cerevisiae: identification of a novel inhibitor of influenza virus. Antimicrob Agents Chemother. 1995 October; 39(10):2204-9 (“BL-1743 does not produce an additive effect on M2 inhibition, suggesting that these two compounds interact with similar sites in the M2 protein . . . . Thus, BL-1743 appears to represent a novel structure with an antiviral profile similar to that of amantadine.”).

SUMMARY

In one aspect of the present invention, provided are compounds having the formula (I):

wherein

A is carbon or nitrogen;

a₁ and a₃ are each independently (CH₂)₁₋₃, CHR₄, C(R₄)₂, CXY, C═S, C═O, or a bond;

a₂ and a₄ are each independently (CH₂)₁₋₃, CHR₄, C(R₄)₂, CXY, or a bond;

R₁ is hydrogen, alkyl, aryl, aralkyl, haloalkyl, amino, alkylamino, —C(R₅)R₆, —R₄(R₅)R₆, —R₄SO₂R₆, —NHCH(acetic acid alkyl ester)R₇, or —R₄NHCH(acetic acid alkyl ester)R₇;

R₂ and R₃ are each independently C₁-C₆ alkyl or haloalkyl,

or,

R₂ and R₃ taken together along with the carbon atom to which they are both attached form a 3- to 8-membered ring optionally substituted with up to three R₄ substituents, and R₂ and R₃ are each independently CH₂, CHR₄, S, or O;

R₄ is C₁-C₆ alkyl, haloalkyl, or aryl;

R₅ is O, S, ═NH, hydroxyl, halo, or amino;

R₆ is hydrogen, alkyl, aryl, aralkyl, amino, alkylamino, or —NHCH(R₄)(R₈);

R₇ is a moiety that contains a hydrogen bond donor;

R₈ is alkylamido or haloalkylamido;

X and Y are each independently halo or deuterium; and,

Z is hydrogen, hydroxyl, halo, C₁-C₆ alkyl, R₁ as defined above, or is absent,

or,

A, R₁, and Z together form a 3- to 8-membered optionally substituted ring;

or a stereoisomer, partial stereoisomer, prodrug, pharmaceutically acceptable salt, hydrate, solvate, acid hydrate, or N-oxide thereof,

with the proviso that if A is nitrogen, each of a₁, a₂, a₃, and a₄ are —CH₂—, R₂ and R₃ taken together along with the carbon atom to which they are both attached form unsubstituted cyclohexyl, and Z is absent, then R₁ cannot be imidazolinyl; and,

if A is nitrogen, both of a₂ and a₄ are —CH₂—, R₂ and R₃ taken together along with the carbon atom to which they are both attached form unsubstituted cyclohexyl, R₁ is hydrogen, and Z is absent, then a₁ and a₃ cannot both be C═O.

In other aspects, provided are methods treating an influenza A virus-affected disease state or infection comprising the step of administering to a subject in need thereof a composition comprising a compound of formula (I):

wherein

A is carbon or nitrogen;

a₁ and a₃ are each independently (CH₂)₀₋₃, CHR₄, C(R₄)₂, CXY, C═O, or C═S;

a₂ and a₄ are each independently (CH₂)₀₋₃, CHR₄, C(R₄)₂, or CXY;

R₁ is hydrogen, alkyl, aryl, aralkyl, haloalkyl, amino, alkylamino, CH(R₅)R₆, R₄(R₅)R₆, R₄SO₂R₆, —NHCH(acetic acid alkyl ester)R₇ or —R₄NHCH(acetic acid alkyl ester)R₇;

R₂ and R₃ are each independently C₁-C₆ alkyl or haloalkyl,

or,

R₂ and R₃ taken together along with the carbon atom to which they are both attached form a 3- to 8-membered ring optionally substituted with up to three R₄ substituents, and R₂ and R₃ are each independently CH₂, CHR₄, S, or O;

R₄ is C₁-C₆ alkyl, haloalkyl, or aryl;

R₅ is O, S, ═NH, hydroxyl, halo, or amino;

R₆ is hydrogen, alkyl, aryl, aralkyl, amino, alkylamino, or —NHCH(R₄)(R₈);

R₇ is a moiety that contains a hydrogen bond donor;

R₈ is alkylamido or haloalkylamido;

X and Y are each independently halo or deuterium; and,

Z is hydrogen, hydroxyl, halo, C₁-C₆ alkyl, R₁, or is absent,

or,

A, R₁, and Z together form a 3- to 8-membered optionally substituted ring;

or a stereoisomer, partial stereoisomer, prodrug, pharmaceutically acceptable salt, hydrate, solvate, acid hydrate, or N-oxide thereof,

with the proviso that if A is nitrogen, each of a₁, a₂, a₃, and a₄ are —CH₂—, R₂ and R₃ taken together along with the carbon atom to which they are both attached form unsubstituted cyclohexyl, and Z is absent, then R₁ cannot be imidazolinyl.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention may be understood more readily by reference to the following detailed description taken in connection with the accompanying figures and examples, which form a part of this disclosure. It is to be understood that this invention is not limited to the specific products, methods, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of the claimed invention.

The disclosures of each patent, patent application, and publication cited or described in this document are hereby incorporated herein by reference, in their entirety.

As employed above and throughout the disclosure, the following terms and abbreviations, unless otherwise indicated, shall be understood to have the following meanings

In the present disclosure the singular forms “a,” “an,” and “the” include the plural reference, and reference to a particular numerical value includes at least that particular value, unless the context clearly indicates otherwise. Thus, for example, a reference to “a compound” is a reference to one or more of such compounds and equivalents thereof known to those skilled in the art, and so forth. Furthermore, when indicating that a certain chemical moiety “may be” X, Y, or Z, it is not intended by such usage to exclude other choices for the moiety; for example, a statement to the effect that R₁ “may be alkyl, aryl, or amino” does not exclude other choices for R₁, such as halo, aralkyl, and the like.

When values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. As used herein, “about X” (where X is a numerical value) preferably refers to ±10% of the recited value, inclusive. For example, the phrase “about 8” refers to a value of 7.2 to 8.8, inclusive; as another example, the phrase “about 8%” refers to a value of 7.2% to 8.8%, inclusive. Where present, all ranges are inclusive and combinable. For example, when a range of “1 to 5” is recited, the recited range should be construed as including ranges “1 to 4”, “1 to 3”, “1-2”, “1-2 & 4-5”, “1-3 & 5”, and the like. In addition, when a list of alternatives is positively provided, such listing can be interpreted to mean that any of the alternatives may be excluded, e.g., by a negative limitation in the claims. For example, when a range of “1 to 5” is recited, the recited range may be construed as including situations whereby any of 1, 2, 3, 4, or 5 are negatively excluded; thus, a recitation of “1 to 5” may be construed as “1 and 3-5, but not 2”, or simply “wherein 2 is not included.” In another example, when a listing of possible substituents including “hydrogen, alkyl, and aryl” is provided, the recited listing may be construed as including situations whereby any of “hydrogen, alkyl, and aryl” is negatively excluded; thus, a recitation of “hydrogen, alkyl, and aryl” may be construed as “hydrogen and aryl, but not alkyl”, or simply “wherein the substituent is not alkyl”.

Protective groups are abbreviated according to the system disclosed in Greene, T. W. and Wuts, P. G. M., Protective Groups in Organic Synthesis 2d. Ed., Wiley & Sons, 1991, which is incorporated in its entirety herein. For example, “CBZ” or “Cbz” or “Z” stands for carbobenzyloxy or benzyloxycarbonyl, “Boc” or “BOC” represents t-butoxycarbonyl, “Alloc” denotes allyloxycarbonyl, Bz means benzoyl, and “Fmoc” stands for 9-fluorenylmethoxycarbonyl.

As used herein, the terms “component,” “composition of compounds,” “compound,” “drug,” “pharmacologically active agent,” “active agent,” “therapeutic,” “therapy,” “treatment,” or “medicament” are used interchangeably herein to refer to a compound or compounds or composition of matter which, when administered to a subject (human or animal) induces a desired pharmacological and/or physiologic effect by local and/or systemic action.

The abbreviations in the specification correspond to units of measure, techniques, properties, or compounds as follows: “min” means minute(s), “g” means gram(s), “mg” means milligram(s), “μg” means microgram(s), “eq” means equivalent(s), “h” means hour(s), “μL” means microliter(s), “mL” means milliliter(s), “mM” means millimolar, “M” means molar, “mmol” or “mmole” means millimole(s), “cm” means centimeters, “SEM” means standard error of the mean, and “IU” means International Units. “IC₅₀ value” or “IC₅₀” means dose of the compound which results in 50% alleviation or inhibition of the observed condition or effect.

As used herein, “alkyl” refers to an optionally substituted, saturated straight, or branched, hydrocarbon radical having from about 1 to about 20 carbon atoms (and all combinations and subcombinations of ranges and specific numbers of carbon atoms therein). Where appropriate, “alkyl” can mean “alkylene”; for example, if X is —R₁R₂, and R₁ is said to be “alkyl”, then “alkyl” may correctly be interpreted to mean “alkylene”.

“Amino” refers to —NH₂ and may include one or more substituents that replace hydrogen.

As used herein, “aryl”, “arene”, and “aromatic” each refer to an optionally substituted, saturated or unsaturated, monocyclic, polycyclic, or other homo- or heterocyclic aromatic ring system having from about 3 to about 50 ring members (and all combinations and subcombinations of ranges and specific numbers of carbon atoms therein), with from about 5 to about 10 ring atom members being preferred. Such moieties encompass (include) “heteroaryl” and “heteroarene” as defined infra. Where appropriate, “aryl” can mean “arene”; for example, if X is —R₁R₂, and R₁ is said to be “aryl”, then “aryl” may correctly be interpreted to mean “arene”.

As used herein, “alkenyl” refers to an alkyl radical having from about 2 to about 20 carbon atoms and one or more double bonds (and all combinations and subcombinations of ranges and specific numbers of carbon atoms therein), wherein alkyl is as previously defined. In some embodiments, it is preferred that the alkenyl groups have from about 2 to about 6 carbon atoms. Alkenyl groups may be optionally substituted.

As used herein, “aralkyl” refers to alkyl radicals bearing one or more aryl substituents and having from about 4 to about 50 carbon atoms (and all combinations and subcombinations of ranges and specific numbers of carbon atoms therein), wherein aryl and alkyl are as previously defined. In some preferred embodiments, the alkyl moieties of the aralkyl groups have from about 1 to about 4 carbon atoms. In other preferred embodiments, the alkyl moieties have from about 1 to about 3 carbon atoms. Aralkyl groups may be optionally substituted.

“Alkylamino” signifies alkyl-(NH)—, wherein alkyl is as previously described and NH is defined in accordance with the provided definition of amino. “Arylamino” represents aryl-(NH)—, wherein aryl is as defined herein and NH is defined in accordance with the provided definition of amino. Likewise, “aralkylamino” is used to denote aralkyl-(NH)—, wherein aralkyl is as previously defined and NH is defined in accordance with the provided definition of amino. “Alkylamido” refers to alkyl-CH(═O)NH—, wherein alkyl is as previously described. “Alkoxy” as used herein refers to the group R—O— where R is an alkyl group, and alkyl is as previously described. “Aralkoxy” stands for R—O—, wherein R is an aralkyl group as previously defined. “Alkylsulfonyl” means alkyl-SO₂—, wherein alkyl is as previously defined.

As used herein, “alkylene” refers to an optionally branched or substituted bivalent alkyl radical having the general formula —(CH₂)_(n)—, where n is 1 to 10. Non-limiting examples include methylene, trimethylene, pentamethylene, and hexamethylene.

As used herein, “heteroaryl” or “heteroarene” refers to an aryl radical wherein in at least one of the rings, one or more of the carbon atom ring members is independently replaced by a heteroatom group selected from the group consisting of S, O, N, and NH, wherein aryl is as previously defined. Heteroaryl/heteroarene groups having a total of from about 3 to about 14 carbon atom ring members and heteroatom ring members are preferred. Likewise, a “heterocyclic ring” is an aryl radical wherein one or more of the carbon atom ring members may be (but are not necessarily) independently replaced by a heteroatom group selected from the group consisting of S, O, N, and NH. Heterocyclic rings having a total from about 3 to 14 ring members and heteroatom ring members are preferred, but not necessarily present; for example, “heterocyclohexyl” may be a six-membered aryl radical with or without a heteroatom group.

“Halo” and “halogen” each refers to a fluoro, chloro, bromo, or iodo moiety, with fluoro, chloro, or bromo being preferred.

“Haloalkyl” signifies halo-alkyl-wherein alkyl and halo, respectively, are as previously described.

The phrase reading “[moiety] is absent” means that the substituents to which the moiety is attached may be directly attached to each other.

Typically, substituted chemical moieties include one or more substituents that replace hydrogen. Exemplary substituents include, for example, halo (e.g., F, Cl, Br, I), alkyl, cycloalkyl, alkylcycloalkyl, cycloalkylalkyl, alkenyl, alkynyl, aralkyl, aryl, heteroaryl, heteroaralkyl, spiroalkyl, heterocycloalkyl, hydroxyl (—OH), nitro (—NO₂), cyano (—CN), amino (—NH₂), —N-substituted amino (—NHR″), —N,N-disubstituted amino (—N(R″)R″), oxo (═O), carboxy (—COOH), —O—C(═O)R″, —C(═O)R″, —OR″, —C(═O)OR″, -(alkylene)-C(═O)—OR″, —NHC(═O)R″, aminocarbonyl (—C(═O)NH₂), —N-substituted aminocarbonyl (—C(═O)NHR″), —N,N-disubstituted aminocarbonyl (—C(═O)N(R″)R″), thiol, thiolato (—SR″), sulfonic acid (—SO₃H), phosphonic acid (—PO₃H), —P(═O)(OR″)OR″, —S(═O)R″, —S(═O)₂R″, —S(═O)₂NH₂, —S(═O)₂ NHR″, —S(═O)₂NR″R″, —NHS(═O)₂R″, —NR″S(═O)₂R″, —CF₃, —CF₂CF₃, —NHC(═O)NHR″, —NHC(═O)NR″R″, —NR″C(═O)NHR″, —NR″C(═O)NR″R″, —NR″C(═O)R″ and the like. In relation to the aforementioned substituents, each moiety R″ can be, independently, any of H, alkyl, cycloalkyl, alkenyl, aryl, aralkyl, heteroaryl, or heterocycloalkyl, for example.

As used herein, the terms “treatment” or “therapy” (as well as different word forms thereof) includes preventative (e.g., prophylactic), curative or palliative treatment.

As employed above and throughout the disclosure the term “effective amount” refers to an amount effective, at dosages, and for periods of time necessary, to achieve the desired result with respect to the treatment of the relevant disorder, condition, or side effect. It will be appreciated that the effective amount of components of the present invention will vary from patient to patient not only with the particular compound, component or composition selected, the route of administration, and the ability of the components to elicit a desired response in the individual, but also with factors such as the disease state or severity of the condition to be alleviated, hormone levels, age, sex, weight of the individual, the state of being of the patient, and the severity of the pathological condition being treated, concurrent medication or special diets then being followed by the particular patient, and other factors which those skilled in the art will recognize, with the appropriate dosage ultimately being at the discretion of the attendant physician. Dosage regimens may be adjusted to provide the improved therapeutic response. An effective amount is also one in which any toxic or detrimental effects of the components are outweighed by the therapeutically beneficial effects. As an example, the compounds useful in the methods of the present invention are administered at a dosage and for a time such that the level of activation and adhesion activity of platelets is reduced as compared to the level of activity before the start of treatment.

“Pharmaceutically acceptable” refers to those compounds, materials, compositions, and/or dosage forms which are, within the scope of sound medical judgment, suitable for contact with the tissues of human beings and animals without excessive toxicity, irritation, allergic response, or other problem complications commensurate with a reasonable benefit/risk ratio.

Within the present invention, the disclosed compounds may be prepared in the form of pharmaceutically acceptable salts. “Pharmaceutically acceptable salts” refer to derivatives of the disclosed compounds wherein the parent compound is modified by making acid or base salts thereof. Examples of pharmaceutically acceptable salts include, but are not limited to, mineral or organic acid salts of basic residues such as amines; alkali or organic salts of acidic residues such as carboxylic acids; and the like. The pharmaceutically acceptable salts include the conventional non-toxic salts or the quaternary ammonium salts of the parent compound formed, for example, from non-toxic inorganic or organic acids. For example, such conventional non-toxic salts include those derived from inorganic acids such as hydrochloric, hydrobromic, sulfuric, sulfamic, phosphoric, nitric and the like; and the salts prepared from organic acids such as acetic, propionic, succinic, glycolic, stearic, lactic, malic, tartaric, citric, ascorbic, pamoic, maleic, hydroxymaleic, phenylacetic, glutamic, benzoic, salicylic, sulfanilic, 2-acetoxybenzoic, fumaric, toluenesulfonic, methanesulfonic, ethane disulfonic, oxalic, isethionic, and the like. These physiologically acceptable salts are prepared by methods known in the art, e.g., by dissolving the free amine bases with an excess of the acid in aqueous alcohol, or neutralizing a free carboxylic acid with an alkali metal base such as a hydroxide, or with an amine.

Compounds described herein throughout, can be used or prepared in alternate forms. For example, many amino-containing compounds can be used or prepared as an acid addition salt. Often such salts improve isolation and handling properties of the compound. For example, depending on the reagents, reaction conditions and the like, compounds as described herein can be used or prepared, for example, as their hydrochloride or tosylate salts. Isomorphic crystalline forms, all chiral and racemic forms, N-oxide, hydrates, solvates, and acid salt hydrates, are also contemplated to be within the scope of the present invention.

Certain acidic or basic compounds of the present invention may exist as zwitterions. All forms of the compounds, including free acid, free base and zwitterions, are contemplated to be within the scope of the present invention. It is well known in the art that compounds containing both amino and carboxy groups often exist in equilibrium with their zwitterionic forms. Thus, any of the compounds described herein throughout that contain, for example, both amino and carboxy groups, also include reference to their corresponding zwitterions.

“Hydrate” refers to a compound of the present invention which is associated with water in the molecular form, i.e., in which the H—OH bond is not split, and may be represented, for example, by the formula R.H₂O, where R is a compound of the invention. A given compound may form more than one hydrate including, for example, monohydrates (R.H₂O) or polyhydrates (R.nH₂O wherein n is an integer >1) including, for example, dihydrates (R.2H₂O), trihydrates (R.3H₂O), and the like, or hemihydrates, such as, for example, R.n/₂H₂O, R.n/₃H₂O, R.n/₄H₂O and the like wherein n is an integer.

“Solvate” refers to a compound of the present invention which is associated with solvent in the molecular form, i.e., in which the solvent is coordinatively bound, and may be represented, for example, by the formula R.(solvent), where R is a compound of the invention. A given compound may form more than one solvate including, for example, monosolvates (R.(solvent)) or polysolvates (R.n(solvent)) wherein n is an integer >1) including, for example, disolvates (R.2(solvent)), trisolvates (R.3(solvent)), and the like, or hemisolvates, such as, for example, R.n/₂(solvent), R.n/₃(solvent), R.n/₄(solvent) and the like wherein n is an integer. Solvents herein include mixed solvents, for example, methanol/water, and as such, the solvates may incorporate one or more solvents within the solvate.

“Acid hydrate” refers to a complex that may be formed through association of a compound having one or more base moieties with at least one compound having one or more acid moieties or through association of a compound having one or more acid moieties with at least one compound having one or more base moieties, said complex being further associated with water molecules so as to form a hydrate, wherein said hydrate is as previously defined and R represents the complex herein described above.

The term “stereoisomers” refers to compounds that have identical chemical constitution, but differ as regards the arrangement of the atoms or groups in space.

“Racemic” means having the capacity for resolution into forms of opposed optical activity.

As used herein, the term “partial stereoisomer” refers to stereoisomers having two or more chiral centers wherein at least one of the chiral centers has defined stereochemistry (i.e., R or S) and at least one has undefined stereochemistry (i.e., R or S). When the term “partial stereoisomers thereof” is used herein, it refers to any compound within the described genus whose configuration at chiral centers with defined stereochemistry centers is maintained and the configuration of each undefined chiral center is independently selected from R or S. For example, if a stereoisomer has three chiral centers and the stereochemical configuration of the first center is defined as having “S” stereochemistry, the term “or partial stereoisomer thereof” refers to stereoisomers having SRR, SRS, SSR, or SSS configurations at the three chiral centers, and mixtures thereof.

“Prodrug” refers to compounds which are themselves inactive or minimally active for the activity desired, but through biotransformation can be converted into biologically active metabolites. For example, a prodrug of the present invention would include, inter alia, any compound which is convertible in vivo by metabolic means to a compound claimed or described in the present disclosure.

“N-oxide” refers to compounds wherein the basic nitrogen atom of either a heteroaromatic ring or tertiary amine is oxidized to give a quaternary nitrogen bearing a positive formal charge and an attached oxygen atom bearing a negative formal charge.

When any variable occurs more than one time in any constituent or in any formula, its definition in each occurrence is independent of its definition at every other occurrence. Combinations of substituents and/or variables are permissible only if such combinations result in stable compounds.

The term “administering” means either directly administering a compound or composition of the present invention, or administering a prodrug, derivative or analog which will form an equivalent amount of the active compound or substance within the body.

“Dosage unit” refers to physically discrete units suited as unitary dosages for the particular individual to be treated. Each unit may contain a predetermined quantity of active compound(s) calculated to produce the desired therapeutic effect(s) in association with the required pharmaceutical carrier. The specification for the dosage unit forms of the invention may be dictated by (a) the unique characteristics of the active compound(s) and the particular therapeutic effect(s) to be achieved, and (b) the limitations inherent in the art of compounding such active compound(s).

“Subject” or “patient” refers to an embryonic, immature, or adult animal, including the human species, that is treatable with the compositions, and/or methods of the present invention.

Accordingly, in one aspect there are provided compounds having the formula (I):

wherein

A is carbon or nitrogen;

a₁ and a₃ are each independently (CH₂)₁₋₃, CHR₄, C(R₄)₂, CXY, C═S, C═O, or a bond;

a₂ and a₄ are each independently (CH₂)₁₋₃, CHR₄, C(R₄)₂, CXY, or a bond;

R₁ is hydrogen, alkyl, aryl, aralkyl, haloalkyl, amino, alkylamino, C(R₅)R₆, R₄(R₅)R₆, R₄SO₂R₆, —NHCH(acetic acid alkyl ester)R₇, or —R₄NHCH(acetic acid alkyl ester)R₇;

R₂ and R₃ are each independently C₁-C₆ alkyl or haloalkyl,

or,

R₂ and R₃ taken together along with the carbon atom to which they are both attached form a 3- to 8-membered ring optionally substituted with up to three R₄ substituents, and R₂ and R₃ are each independently CH₂, CHR₄, S, or O;

R₄ is C₁-C₆ alkyl, haloalkyl, or aryl;

R₅ is O, S, ═NH, hydroxyl, halo, or amino;

R₆ is hydrogen, alkyl, aryl, aralkyl, amino, alkylamino, or —NHCH(R₄)(R₈);

R₇ is a moiety that contains a hydrogen bond donor;

R₈ is alkylamido or haloalkylamido;

X and Y are each independently halo or deuterium; and,

Z is hydrogen, hydroxyl, halo, C₁-C₆ alkyl, R₁ as defined above, or is absent,

or,

A, R₁, and Z together form a 3- to 8-membered optionally substituted ring;

or a stereoisomer, partial stereoisomer, prodrug, pharmaceutically acceptable salt, hydrate, solvate, acid hydrate, or N-oxide thereof,

with the proviso that if A is nitrogen, each of a₁, a₂, a₃, and a₄ are —CH₂—, R₂ and R₃ taken together along with the carbon atom to which they are both attached form unsubstituted cyclohexyl, and Z is absent, then R₁ cannot be imidazolinyl; and,

if A is nitrogen, both of a₂ and a₄ are —CH₂—, R₂ and R₃ taken together along with the carbon atom to which they are both attached form unsubstituted cyclohexyl, R₁ is hydrogen, and Z is absent, then a₁ and a₃ cannot both be C═O.

Each of a₁, a₂, a₃, and a₄ may be —CH₂—, and in such instances, R₂ and R₃ may each be alkyl. For example, the compound may be 4,4-Dimethyl-piperidine.

In other embodiments R₂ and R₃ may be taken together along with the carbon atom to which they are both attached form a 3- to 8-membered ring. For example, R₂ and R₃ taken together along with the carbon atom to which they are both attached may form heterocyclopentyl or heterocyclohexyl.

With respect to the compounds of formula (I), A may be nitrogen.

In such instances, a₃ may be a single bond. For example, the compound may be 2-Aza-spiro[4.5]decane.

In other embodiments, each of a₁, a₂, a₃, and a₄ may be —CH₂—. With respect to such embodiments, R₁ may be hydrogen or alkyl. For example, the compound may be 3-Methyl-3-aza-spiro[5.5]undecane, 8-Aza-spiro[4.5]decane, or 3-Aza-spiro[5.5]undecane. In other instances, R₁ may be aryl or aralkyl. For example, the compound may be 8-(4,5-Dihydro-1H-imidazol-2-yl)-8-aza-spiro[4.5]decane, or 3-(3H-Imidazol-4-ylmethyl)-3-aza-spiro[5.5]undecane. R₁ may also be CH(R₅)R₆. In such instances, R₆ may be amino. For example, the compound may be 3-Aza-spiro[5.5]undecane-3-carboxylic acid amide, 3-Aza-spiro[5.5]undecane-3-carbothioic acid amide, or 3-Aza-spiro[5.5]undecane-3-carboxamidine.

With respect to the compounds of formula (I), A may be carbon.

When A is carbon, each of a₁, a₂, a₃, and a₄ may be —CH₂—. In some embodiments of this variety, A, R₁, and Z may together form a 3- to 8-membered optionally substituted ring. A, R₁, and Z may together form imidazolidin-4-one, optionally substituted with up to three substituents independently selected from alkyl, halo, haloakyl, aryl, aralkyl, amino, and aminoalkyl. For example, the compound may be represented by the formula:

wherein R₄ is as defined above with respect to formula (I).

In other embodiments wherein A is carbon and each of a₁, a₂, a₃, and a₄ is —CH₂—, R₂ and R₃ may be taken together along with the carbon atom to which they are both attached to form heterocyclopentyl or heterocyclohexyl. In yet other embodiments, R₁ may be aryl, amino, or alkylamino. For example, the compound may be Spiro[5.5]undec-3-ylamine, or

Methyl-spiro[5.5]undec-3-yl-amine. Where R₁ is aryl, amino, or alkylamino, Z may be, inter alia, hydrogen or hydroxyl. For example, the compound may be 3-(3H-Imidazol-4-yl)-spiro[5.5]undecan-3-ol, or 5-Spiro[5.5]undec-3-yl-1H-imidazole.

In other embodiments wherein A is carbon and each of a₁, a₂, a₃, and a₄ is —CH₂—, R₁ may be CH(R₅)R₆. In such instances, R₅ may be halo or hydroxyl, and/or R₆ may be aryl. For example, the compound may be (3-Aza-spiro[5.5]undec-3-yl)-(3H-imidazol-4-yl)-methanol, or 3-[Fluoro-(3H-imidazol-4-yl)-methyl]-3-aza-spiro[5.5]undecane. In other embodiments, R₅ may be O, S, or ═NH, and R₆ may be —NHCH(R₄)(R₈), wherein R₄ is as defined above with respect to the compound of formula (I) and R₈ is alkylamido or haloalkylamido. For example, the compound may be represented by the formula:

wherein R₄ is as defined above with respect to formula (I).

In yet other embodiments wherein A is carbon and each of a₁, a₂, a₃, and a₄ is —CH₂—, R₁ may be —NHCH(acetic acid alkyl ester)R₇. R₇ may be a side chain of an amino acid that contains an H-bond donor. Nonlimiting examples of amino acid side chains that contain H-bond donors include the arginine side chain and the histidine side chain. For example, the compound may be 3-(1H-Imidazol-4-yl)-2-(spiro[5.5]undec-3-ylamino)-propionic acid methyl ester or, 5-Guanidino-2-(spiro[5.5]undec-3-ylamino)-pentanoic acid methyl ester.

The compounds employed in the present invention may exist in prodrug form. As used herein, “prodrug” is intended to include any covalently bonded carriers which release the active parent drug, for example, as according to the formulas or compounds employed in the methods of the present invention in vivo when such prodrug is administered to a subject. Since prodrugs are known to enhance numerous desirable qualities of pharmaceuticals (e.g., solubility, bioavailability, manufacturing, etc.) the compounds of the present invention may, if desired, be delivered in prodrug form. Thus, the present invention contemplates methods of delivering prodrugs. Prodrugs of the compounds employed in the present invention, for example, according to formula (I), may be prepared by modifying functional groups present in the compound in such a way that the modifications are cleaved, either in routine manipulation or in vivo, to the parent compound.

Accordingly, prodrugs include, for example, compounds described herein in which a hydroxy, amino, or carboxy group is bonded to any group that, when the prodrug is administered to a mammalian subject, cleaves to form a free hydroxyl, free amino, or carboxylic acid, respectively. Examples include, but are not limited to, acetate, formate and benzoate derivatives of alcohol and amine functional groups; and alkyl, carbocyclic, aryl, and alkylaryl esters such as methyl, ethyl, propyl, iso-propyl, butyl, isobutyl, sec-butyl, tert-butyl, cyclopropyl, phenyl, benzyl, and phenethyl esters, and the like.

As will be readily understood, functional groups present may contain protecting groups during the course of synthesis. Protecting groups are known per se as chemical functional groups that can be selectively appended to and removed from functionalities, such as hydroxyl groups and carboxyl groups. These groups are present in a chemical compound to render such functionality inert to chemical reaction conditions to which the compound is exposed. Any of a variety of protecting groups may be employed with the present invention. Protecting groups that may be employed in accordance with the present invention may be described in Greene, T. W. and Wuts, P. G. M., Protective Groups in Organic Synthesis 2d. Ed., Wiley & Sons, 1991.

In a further aspect, the invention relates to pharmaceutical compositions comprising a compound according to formula (I) and a pharmaceutically acceptable carrier, diluent, or excipient. The applicable carrier, diluent, or excipient may be selected on the basis of the chosen route of administration and standard pharmaceutical practice as described, for example, in Remington's Pharmaceutical Sciences (Mack Pub. Co., Easton, Pa., 1985), the disclosure of which is hereby incorporated by reference in its entirety.

Also provided are methods for treating an influenza A virus-affected disease state or infection comprising the step of administering to a subject in need thereof a composition comprising a compound of formula (I):

wherein

A is carbon or nitrogen;

a₁ and a₃ are each independently (CH₂)₀₋₃, CHR₄, C(R₄)₂, CXY, C═O, or C═S;

a₂ and a₄ are each independently (CH₂)₀₋₃, CHR₄, C(R₄)₂, or CXY;

R₁ is hydrogen, alkyl, aryl, aralkyl, haloalkyl, amino, alkylamino, CH(R₅)R₆, R₄(R₅)R₆, R₄SO₂R₆, —NHCH(acetic acid alkyl ester)R₇, or —R₄NHCH(acetic acid alkyl ester)R₇;

R₂ and R₃ are each independently C₁-C₆ alkyl or haloalkyl,

or,

R₂ and R₃ taken together along with the carbon atom to which they are both attached form a 3- to 8-membered ring optionally substituted with up to three R₄ substituents, and R₂ and R₃ are each independently CH₂, CHR₄, S, or O;

R₄ is C₁-C₆ alkyl or haloalkyl;

R₅ is O, S, ═NH, hydroxyl, halo, or amino;

R₆ is hydrogen, alkyl, aryl, aralkyl, amino, alkylamino, or —NHCH(R₄)(R₈);

R₇ is a moiety that contains a hydrogen bond donor;

R₈ is alkylamido or haloalkylamido;

X and Y are each independently halo or deuterium; and,

Z is hydrogen, hydroxyl, halo, C₁-C₆ alkyl, R₁, or is absent,

or,

A, R₁, and Z together form a 3- to 8-membered optionally substituted ring;

or a stereoisomer, partial stereoisomer, prodrug, pharmaceutically acceptable salt, hydrate, solvate, acid hydrate, or N-oxide thereof,

with the proviso that if A is nitrogen, each of a₁, a₂, a₃, and a₄ are —CH₂—, R₂ and R₃ taken together along with the carbon atom to which they are both attached form unsubstituted cyclohexyl, and Z is absent, then R₁ cannot be imidazolinyl.

The influenza A virus-affected disease state or infection may comprise any condition that arises as a direct or indirect result of the presence of influenza A virus. For example, the influenza A virus-affected disease state may comprise influenza (flu), pneumonia, bronchitis, sinus infection, or ear infection, among other conditions.

Each of a₁, a₂, a₃, and a₄ may be —CH₂—, and in such instances, R₂ and R₃ may each be alkyl. For example, the compound may be 4,4-Dimethyl-piperidine.

In other embodiments of the present methods R₂ and R₃ may be taken together along with the carbon atom to which they are both attached form a 3- to 8-membered ring. For example, R₂ and R₃ taken together along with the carbon atom to which they are both attached may form heterocyclopentyl or heterocyclohexyl.

With respect to the compounds of formula (I), A may be nitrogen.

In such instances, a₃ may be a single bond. For example, the compound may be 2-Aza-spiro[4.5]decane.

In other embodiments of the present methods, a₁ and a₃ may both be C═O. In such instances, R₁ may be hydrogen. For example, the compound that is administered pursuant to the present methods may be 3-Aza-spiro[5.5]undecane-2,4-dione.

In other embodiments of the present methods, each of a₁, a₂, a₃, and a₄ may be —CH₂—. With respect to such embodiments, R₁ may be hydrogen or alkyl. For example, the compound may be 3-Methyl-3-aza-spiro[5.5]undecane, 8-Aza-spiro[4.5]decane, or 3-Aza-spiro[5.5]undecane. In other instances, R₁ may be aryl or aralkyl. For example, the compound may be 8-(4,5-Dihydro-1H-imidazol-2-yl)-8-aza-spiro[4.5]decane, or 3-(3H-Imidazol-4-ylmethyl)-3-aza-spiro[5.5]undecane. R₁ may also be CH(R₅)R₆. In such instances, R₆ may be amino. For example, the compound may be 3-Aza-spiro[5.5]undecane-3-carboxylic acid amide, 3-Aza-spiro[5.5]undecane-3-carbothioic acid amide, or 3-Aza-spiro[5.5]undecane-3-carboxamidine.

With respect to the present methods, in the compound of formula (I), A may be carbon.

When A is carbon, each of a₁, a₂, a₃, and a₄ may be —CH₂—. In some embodiments of this variety, A, R₁, and Z may together form a 3- to 8-membered optionally substituted ring. A, R₁, and Z may together form imidazolidin-4-one, optionally substituted with up to three substituents independently selected from alkyl, halo, haloakyl, aryl, aralkyl, amino, and aminoalkyl. For example, the compound may be represented by the formula:

wherein R₄ is as defined above with respect to formula (I).

In other embodiments of the present methods wherein A is carbon and each of a₁, a₂, a₃, and a₄ is —CH₂—, R₂ and R₃ may be taken together along with the carbon atom to which they are both attached to form heterocyclopentyl or heterocyclohexyl. In yet other embodiments, R₁ may be aryl, amino, or alkylamino. For example, the compound may be Spiro[5.5]undec-3-ylamine, or Methyl-spiro[5.5]undec-3-yl-amine. Where R₁ is aryl, amino, or alkylamino, Z may be, inter alia, hydrogen or hydroxyl. For example, the compound may be 3-(3H-Imidazol-4-yl)-spiro[5.5]undecan-3-ol, or 5-Spiro[5.5]undec-3-yl-1H-imidazole.

In other embodiments of the present methods wherein A is carbon and each of a₁, a₂, a₃, and a₄ is —CH₂—, R₁ may be CH(R₅)R₆. In such instances, R₅ may be halo or hydroxyl, and/or R₆ may be aryl. For example, the compound may be (3-Aza-spiro[5.5]undec-3-yl)-(3H-imidazol-4-yl)-methanol, or 3-[Fluoro-(3H-imidazol-4-yl)-methyl]-3-aza-spiro[5.5]undecane. In other embodiments, R₅ may be O, S, or ═NH, and R₆ may be —NHCH(R₄)(R₈), wherein R₄ is as defined above with respect to the compound of formula (I) and R₈ is alkylamido or haloalkylamido. For example, the compound may be represented by the formula:

wherein R₄ is as defined above with respect to formula (I).

In yet other embodiments of the present methods wherein A is carbon and each of a₁, a₂, a₃, and a₄ is —CH₂—, R₁ may be —NHCH(acetic acid alkyl ester)R₇. R₇ may be a side chain of an amino acid that contains an H-bond donor. Nonlimiting examples of amino acid side chains that contain H-bond donors include the arginine side chain and the histidine side chain. For example, the compound may be 3-(1H-Imidazol-4-yl)-2-(spiro[5.5]undec-3-ylamino)-propionic acid methyl ester or, 5-Guanidino-2-(spiro[5.5]undec-3-ylamino)-pentanoic acid methyl ester.

The compounds of this invention may be administered orally or parenterally, neat or in combination with conventional pharmaceutical carriers, diluents, or excipients, which may be liquid or solid. The applicable solid carrier, diluent, or excipient may function as, among other things, a binder, disintegrant, filler, lubricant, glidant, compression aid, processing aid, color, sweetener, preservative, suspensing/dispersing agent, tablet-disintegrating agent, encapsulating material, film former or coating, flavors, or printing ink. Of course, any material used in preparing any dosage unit form is preferably pharmaceutically pure and substantially non-toxic in the amounts employed. In addition, the active compound may be incorporated into sustained-release preparations and formulations. Parenteral administration in this respect includes administration by, inter alia, the following routes: intravenous, intramuscular, subcutaneous, intraocular, intrasynovial, transepithelial including transdermal, ophthalmic, sublingual and buccal; topically including ophthalmic, dermal, ocular, rectal and nasal inhalation via insufflation, aerosol, and rectal systemic.

In powders, the carrier, diluent, or excipient may be a finely divided solid that is in admixture with the finely divided active ingredient. In tablets, the active ingredient is mixed with a carrier, diluent or excipient having the necessary compression properties in suitable proportions and compacted in the shape and size desired. For oral therapeutic administration, the active compound may be incorporated with the carrier, diluent, or excipient and used in the form of ingestible tablets, buccal tablets, troches, capsules, elixirs, suspensions, syrups, wafers, and the like. The amount of active compound(s) in such therapeutically useful compositions is preferably such that a suitable dosage will be obtained. The therapeutic compositions preferably contain up to about 99% of the active ingredient.

Liquid carriers, diluents, or excipients may be used in preparing solutions, suspensions, emulsions, syrups, elixirs, and the like. The active ingredient of this invention can be dissolved or suspended in a pharmaceutically acceptable liquid such as water, an organic solvent, a mixture of both, or pharmaceutically acceptable oils or fat. The liquid carrier, excipient, or diluent can contain other suitable pharmaceutical additives such as solubilizers, emulsifiers, buffers, preservatives, sweeteners, flavoring agents, suspending agents, thickening agents, colors, viscosity regulators, stabilizers, or osmo-regulators.

Suitable solid carriers, diluents, and excipients may include, for example, calcium phosphate, silicon dioxide, magnesium stearate, talc, sugars, lactose, dextrin, starch, gelatin, cellulose, methyl cellulose, ethylcellulose, sodium carboxymethyl cellulose, microcrystalline cellulose, polyvinylpyrrolidine, low melting waxes, ion exchange resins, croscarmellose carbon, acacia, pregelatinized starch, crospovidone, HPMC, povidone, titanium dioxide, polycrystalline cellulose, aluminum methahydroxide, agar-agar, tragacanth, or mixtures thereof.

Suitable examples of liquid carriers, diluents and excipients for oral and parenteral administration include water (particularly containing additives as above, e.g. cellulose derivatives, preferably sodium carboxymethyl cellulose solution), alcohols (including monohydric alcohols and polyhydric alcohols, e.g. glycols) and their derivatives, and oils (e.g. fractionated coconut oil and arachis oil), or mixtures thereof.

For parenteral administration, the carrier, diluent, or excipient can also be an oily ester such as ethyl oleate and isopropyl myristate. Also contemplated are sterile liquid carriers, diluents, or excipients, which are used in sterile liquid form compositions for parenteral administration. Solutions of the active compounds as free bases or pharmacologically acceptable salts can be prepared in water suitably mixed with a surfactant, such as hydroxypropylcellulose. A dispersion can also be prepared in glycerol, liquid polyethylene glycols, and mixtures thereof and in oils. Under ordinary conditions of storage and use, these preparations may contain a preservative to prevent the growth of microorganisms.

The pharmaceutical forms suitable for injectable use include, for example, sterile aqueous solutions or dispersions and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersions. In all cases, the form is preferably sterile and fluid to provide easy syringability. It is preferably stable under the conditions of manufacture and storage and is preferably preserved against the contaminating action of microorganisms such as bacteria and fungi. The carrier, diluent, or excipient may be a solvent or dispersion medium containing, for example, water, ethanol, polyol (for example, glycerol, propylene glycol, liquid polyethylene glycol and the like), suitable mixtures thereof, and vegetable oils. The proper fluidity can be maintained, for example, by the use of a coating, such as lecithin, by the maintenance of the required particle size in the case of a dispersion, and by the use of surfactants. The prevention of the action of microorganisms may be achieved by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, sorbic acid, thimerosal and the like. In many cases, it will be preferable to include isotonic agents, for example, sugars or sodium chloride. Prolonged absorption of the injectable compositions may be achieved by the use of agents delaying absorption, for example, aluminum monostearate and gelatin.

Sterile injectable solutions may be prepared by incorporating the active compounds in the required amounts, in the appropriate solvent, with various of the other ingredients enumerated above, as required, followed by filtered sterilization. Generally, dispersions may be prepared by incorporating the sterilized active ingredient into a sterile vehicle which contains the basic dispersion medium and the required other ingredients from those enumerated above. In the case of sterile powders for the preparation of sterile injectable solutions, the preferred methods of preparation may include vacuum drying and the freeze drying technique that yields a powder of the active ingredient or ingredients, plus any additional desired ingredient from the previously sterile-filtered solution thereof.

The compounds of the invention may be administered in an effective amount by any of the conventional techniques well-established in the medical field. The compounds employed in the methods of the present invention including, for example, the compounds of formula I or II may be administered by any means that results in the contact of the active agents with the agents' site or sites of action in the body of a patient. The compounds may be administered by any conventional means available.

Preferably the pharmaceutical composition is in unit dosage form, e.g. as tablets, buccal tablets, troches, capsules, elixirs, powders, solutions, suspensions, emulsions, syrups, wafers, granules, suppositories, or the like. In such form, the composition is sub-divided in unit dose containing appropriate quantities of the active ingredient; the unit dosage forms can be packaged compositions, for example packeted powders, vials, ampoules, prefilled syringes or sachets containing liquids. The unit dosage form can be, for example, a capsule or tablet itself, or it can be the appropriate number of any such compositions in package form. In addition, dosage forms of the present invention can be in the form of capsules wherein one active ingredient is compressed into a tablet or in the form of a plurality of microtablets, particles, granules or non-perils. These microtablets, particles, granules or non-perils are then placed into a capsule or compressed into a capsule, possibly along with a granulation of the another active ingredient.

The dosage of the compounds of the present invention that will be most suitable for prophylaxis or treatment will vary with the form of administration, the particular compound chosen and the physiological characteristics of the particular patient under treatment. Generally, small dosages may be used initially and, if necessary, increased by small increments until the desired effect under the circumstances is reached. Generally speaking, oral administration may require higher dosages.

The desired dose may conveniently be presented in a single dose or as divided doses administered at appropriate intervals, for example, as two, three, four or more sub-doses per day. The sub-dose itself may be further divided, e.g., into a number of discrete loosely spaced administrations. The dose may also be provided by controlled release of the compound, by techniques well known to those in the art.

The compounds useful in the methods of the present invention may be prepared in a number of ways well known to those skilled in the art. The compounds can be synthesized, for example, by the methods as described below, or variations thereon as appreciated by the skilled artisan. The reagents used in the preparation of the compounds of this invention can be either commercially obtained or can be prepared by standard procedures described in the literature. All processes disclosed in association with the present invention are contemplated to be practiced on any scale, including milligram, gram, multigram, kilogram, multikilogram or commercial industrial scale.

The present invention is further defined in the following Examples. It should be understood that these examples, while indicating preferred embodiments of the invention, are given by way of illustration only, and should not be construed as limiting the appended claims From the above discussion and these examples, one skilled in the art can ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.

EXAMPLES

All chemicals for use in preparing the inventive compounds were purchased from commercial vendors and used without further purification, unless otherwise noted. 3,3-Pentamethylene glutarimide was purchased from Bosche Scientific, LLC (New Brunswick, N.J.). ¹HNMR and ¹³CNMR spectra were recorded on a DMX-360 NMR spectrometer. Chemical shifts are reported in parts per million referenced with respect to residual solvent (CHCl₃=7.26 ppm and DMSO-d6=2.50 ppm) or from internal standard tetramethylsilane (TMS=0.00 ppm). The following abbreviations were used in reporting spectra: s=singlet, d=doublet, t=triplet, q=quartet, m=multiplet, dd=doublet of doublets. All reactions were carried out under N₂ atmosphere, unless otherwise stated. HPLC grade solvents were used for all the reactions. Column chromatography was performed using silica gel (230-400 mesh). Low-resolution mass spectra were obtained on an LC platform from Micromass using ESI technique.

Example 1 Synthesis of and NMR/Mass Spectrometry Data for Exemplary Influenza A M2 Proton Channel Inhibitors

Synthesis of some preferred embodiments (compounds 1-7) was accomplished as illustrated in the following generalized schematic and as described below:

Reduction of 3,3-Pentamethylene glutarimide with LiAlH₄ in refluxing THF gave 3-azaspiro[5,5]undecane (2) in 82% yield, subsequent nucleophilic substitution of 2-methylthio-2-imidazoline furnished the model compound BL-1743 (1). Methylation was achieved by reductive amination of 2 with formaldehyde using NaBH(OAc)₃/AcOH in dicholoroethane as reported. Subsequent treatment of 2 with trimethylsilyl isocyanate, trityl thioisocyanate and 1,3-diBoc-2-methyl-2-thiopseudourea, followed by deprotection gave carboxamide (4), carbothioamide (5) carboximidamide (7) respectively. Synthesis of sulfonamide (6) was achieved using the literature reported sulfamoylating agent.

3 3-Aza-spiro[5.5]undecane (2)

To a solution of the LiAlH₄ (0.38 g, 10 mmol) in THF (20 ml) at 0° C. was added 3,3-Pentamethylene glutarimide (0.36 g, 2 mmol) in THF (10 ml) dropwise under a nitrogen atmosphere. The reaction was allowed to warm to RT over 30 mins, then refluxing overnight. The solution was cooled to 0° C. and quenched with H₂O (0.38 ml), 15% NaOH (0.38 ml), and H₂O (1.14 ml) sequentially. The resulting slurry was filtered. The filtrate was diluted with CH₂Cl₂ and washed with brine, dried (MgSO₄), filtered, and concentrated in vacuo and purified by flash chromatography to give 3-azaspiro[5,5]undecane as yellow oil. Hydrochloride salt was made by purging HCl gas into the ether solution of 3-azaspiro[5,5]undecane at 0° C., followed by decant the ether supernatant, the final white solid (0.28 g) was dried in vacuo. Yield (75%).¹H-NMR (360 MHz, CDCl₃) δ 9.29 (br s, 2H), 3.14 (t, J=5.87 Hz, 4H), 1.74 (t, J=5.87 Hz, 4H), 1.43 (m, 10H); ¹³C-NMR (90 MHz, CDCl₃) δ 39.93, 35.85, 32.76, 30.60, 26.53, 21.37; ESI-MS: m/z+[M+H]⁺=154.5.

3-(4,5-dihydro-1H-imidazol-2-yl)-3-azaspiro[5.5]undecane hydroiodide (BL-1743, 1)

3-azaspiro[5,5]undecane (0.38 g, 2 mmol) and 2-methylthio-2-imidazoline hydrocholoride (0.44 g, 1.8 mmol) was refluxing in CH₃OH overnight, concentrated in vacuo and purified by flash chromatography to give yellow oil (0.26 g). Yield (65%). ¹H-NMR (360 MHz, CDCl₃) δ 3.72 (s, 4H), 3.39 (t, J=5.94 Hz, 4H), 1.55 (t, J=5.94 Hz, 4H), 1.47-1.44 (m, 10H); ¹³C-NMR (90 MHz, CDCl₃) δ 159.48, 43.39, 42.73, 36.02, 35.26, 30.83, 26.65, 21.61. 21.49; ESI-MS: m/z [M+H]⁺=222.5.

3-methyl-3-azoniaspiro[5.5]undecane chloride (3)

To a solution of 3-azaspiro[5,5]undecane (0.38 g, 2 mmol), formaldehyde (0.15 g 5 mmol) and NaBH(OAc)₃ (0.42 g, 2 mmol) in dicholoethane (10 ml) were added AcOH (0.12 g, 2 mmol), the resulting suspension was stirred overnight, diluted with NaHCO₃ and extracted with CH₂Cl₂ twice, washed with brine, and dried with MgSO₄. The solution was filtered, concentrated in vacuo and purified by flash chromatography. Hydrochloride salt was made by purging HCl gas into the ether solution of 3-methyl-3-azoniaspiro[5.5]undecane at 0° C., followed by decant the ether supernatant, the final white solid (0.33 g) was dried in vacuo. Yield (80%) ¹H-NMR (360 MHz, CDCl₃) δ 3.35-3.31 (m, 2H), 2.83-2.79 (m, 2H), 2.75 (S, 3H), 2.10-2.00 (m, 2H), 1.77-1.74 (m, 2H); ¹³C-NMR (90 MHz, CDCl₃) δ 50.56, 43.69, 39.69, 32.91, 31.43, 26.49, 21.55; ESI-MS: m/z [M+H]⁺=168.6.

3-Aza-spiro[5.5]undecane-3-carboxylic acid amide (4)

Triethylamine (0.42 ml, 3 mmol) was added to 3-azaspiro[5,5]undecane (0.38 g, 2 mmol) in CH₂Cl₂ (10 ml) at 0° C., then trimethylsilyl isocyanate (0.35 g, 3 mmol) was added dropwise to the solution under N₂, the solution was allowed to warm to RT and stirred for 7 hrs. H₂O was added and the solution was extracted with CHCl₃ twice, the combined organic layer was dried with MgSO₄, filtered, concentrated in vacuo and purified by flash column to give white powder (0.32 g). Yield (82%) ¹H-NMR (360 MHz, CD₃CN) δ 5.23 (br s, 2H), 3.31 (t, J=5.87 Hz, 4H), 1.46-1.36 (m, 14H); ¹³C-NMR (90 MHz, CD₃CN) δ 160.23, 41.09, 37.21, 36.95, 27.87. 22.57, 21.83; ESI-MS: m/z [M−H]⁻=195.1.

3-Aza-spiro[5,5]undecane-3-carbothioic acid amide (5)

3-azaspiro[5,5]undecane (0.38 g, 2 mmol) and trityl isothiocyanate (0.54 g, 1.8 mmol) was stirred in THF at RT for 8 hrs until the disappearance of trityl isothiocyanate based in TLC, then the mixture was concentrated in vacuo and purified by flash column (hexane/CHCl₃=1:1 to CHCl₃) to give white foam. This was followed by deprotection of trityl group using 20% TFA/CH₂Cl₂ for 2 hrs at RT. TFA was removed by purging N₂ through the solution to give yellow solid which was subsequently purified by flash column (0.29 g). Yield (76%) ¹H-NMR (360 MHz, CD₃CN) δ 6.04 (br s 2H), 3.70 (s, 4H), 1.48-1.37 (m, 14H), 1.46-1.36 (m, 14H); ¹³C-NMR (90 MHz, CD₃CN) δ 181.49, 45.25, 37.46, 37.08, 32.16, 27.89, 22.73; ESI-MS: m/z [M+Na⁺]⁺=236.8.

3-Aza-spiro[5,5]undecane-3-sulfonic acid amide (6)

The sulfamoylating agent-N-(tert-Butoxycarbonyl)-N-[4-(dimethylazaniumylidene)-1,4-dihydropyridin-1-ylsulfonyl]azanide was synthesized according to literature protocol. See Winum, J. Y.; Toupet, L.; Barragan, V.; Dewynter, G.; Montero, J. L. Organic Letters 2001, 3, 2241-2243. 3-azaspiro[5,5]undecane (0.38 g, 2 mmol) and the sulfamoylating agent (0.602 g, 2 mmol) were stirred in CH₂Cl₂ (10 ml) at RT overnight. Solvent was removed by rotary evaporation and the residue was purified by flash column to give tert-butyl 3-azaspiro[5.5]undecan-3-ylsulfonylcarbamate. The Boc protecting group was removed by 20% TFA/CH₂Cl₂ for 2 hrs at RT. Excess TFA was removed by purging N₂ through the solution to give yellow solid which was subsequently purified by flash column (0.29 g). Yield (62% for 3 steps) ¹H-NMR (360 MHz, CD₃CN) δ 5.01 (br s 2H), 3.03 (t, J=5.78 Hz, 4H), 1.53 (t, J=5.78 Hz, 4H), 1.46-1.35 (m, 10H); ¹³C-NMR (90 MHz, CD₃CN) δ 41.78, 35.62, 35.06, 26.41, 21.06, 20.84; ESI-MS: m/z [M+H⁺]⁺=233.1.

3-Aza-spiro[5,5]undecane-3-carboxamidine (7)

3-azaspiro[5,5]undecane (0.38 g, 2 mmol), HgCl₂ (0.54 g, 2 mmol) and 1,3-Bis(tert-butoxycarbonyl)-2-methyl-2-thiopseudourea (0.58 g, 2 mmol) were stirred in DMF (10 ml) under N₂ atmosphere for 24 hrs, H₂O was added and the white precipitate was removed by filtration, washed with CH₂Cl₂ twice, the combined filtrate was extracted with CH₂Cl₂, washed with brine, dried with MgSO₄, concentrated in vacuo and purified by flash column. The Boc protecting group was removed by 20% TFA/CH₂Cl₂ for 2 hrs at RT. Excess TFA was removed by purging N₂ through the solution to give yellow solid which was subsequently purified by flash column (0.28 g). Yield (71% over two steps). ¹H-NMR (360 MHz, CD₃CN) δ 5.11 (br s 2H), 3.12 (t, J=5.74 Hz, 4H), 1.57 (t, J=5.74 Hz, 4H), 1.46-1.35 (m, 10H); ¹³C-NMR (90 MHz, CD₃CN) δ 157.20, 41.78, 35.64, 35.06, 26.48, 21.26, 20.94; ESI-MS: m/z [M+H⁺]⁺=196.3.

Synthesis reactions for compounds 8-9 were carried out in accordance with the following scheme and description:

Robinson annulation using sulfuric acid as catalyst gave spiro[5.5]undec-1-en-3-one in one port with 85% yield (Flaugh, M. E.; Crowell, T. A.; Farlow, D. S. Journal of Organic Chemistry 1980, 45, 5399-5400). Hydrogenation followed by Leuckart Reaction gave spiro[5.5]undecan-3-amine, further methylation was achieved by reductive amination with NaBH(OAc)₃/AcOH. See AbdelMagid, A. F.; Carson, K. G.; Harris, B. D.; Maryanoff, C. A.; Shah, R. D. Journal of Organic Chemistry 1996, 61, 3849-3862.

Spiro[5.5]undec-3-ylamine (8)

Cyclohexanecarbaldehyde (1.12 g, 10 mmol), but-3-en-2-one (0.70 g, 10 mmol) were refluxing in toluene (10 ml) with catalytic amount H₂SO₄ (0.05 ml) as catalyst in round bottom flask equipped with Dean-Stark trap until no more H₂O condensed from the reaction mixture. After 5 hrs, 50 ml 1M NaHCO₃ was added, organic phase was separated. The aqueous phase was extracted again with toluene, the combined organic phase was washed with brine and dried with MgSO₄, the solid was filtered, concentrated in vacuo to give crude yellow oil which was separated by flash column (CHCl₃/hexane=30%, 50% to 100%). spiro[5.5]undec-1-en-3-one was hydrogenated by Pd/C with H₂ balloon in 3 hrs. Leuckart reaction was carried out by refluxing spiro[5.5]undecan-3-one in excess formamide (6.76 g) and acetic acid (2.30 g) overnight. H₂O was added and the mixture was extracted with ether 3 times, the combined ether was concentrated to give yellow oil. Then 30% HCl was added to the oily residue and refluxed for another 1 hr. The solution was cooled down to RT, neutralized with 30% NaOH to pH˜10, extracted with ether, dried with Mg₂SO₄ and concentrated in vacuo. The crude product was further purified by flash column to give 8 (0.94 g) after HCl/ether treatment as described earlier. Yield (46% for 3 steps) ¹H-NMR (360 MHz, CD₃CN) δ 8.30 (br s, 3H), 2.76 (m, 1H), 1.95-1.70 (m, 8H), 1.46-1.38 (m, 8H), 1.27-1.21 (m, 2H); ¹³C-NMR (90 MHz, CD₃CN) 6 NO; ESI-MS: m/z [M+H⁺]⁺=168.5.

Methyl-spiro[5.5]undec-3-yl-amine (9)

Compound 9 was synthesized by reductive aminaiton of 8 under the same condition as described earlier. Yield (78%) ¹H-NMR (360 MHz, CD₃CN) δ 9.45 (br s, 2H), 3.74-3.71 (m, 1H), 2.64 (t, J=5.67 Hz, 3H), 1.97-1.80 (m, 4H), 1.63-1.43 (m, 8H), 1.23-1.20 (m, 2H), 1.11-1.06 (m, 2H); ¹³C-NMR (90 MHz, CD₃CN) δ 59.26, 40.73, 34.58, 32.16, 30.06, 26.94, 24.30, 21.98; ESI-MS: m/z [M+H⁺]⁺=182.5.

Synthesis reactions for compounds 10-11 were carried out in accordance with the following scheme and description:

3-Aza-spiro[5.5]undecane-7,11-dione (10)

4-Piperidone hydrochloride (0.31 g, 2 mmol), 1,3-propanediol (0.76 g, 10 mmol) and phosphoric acid (0.5 g) were stirred at 65° C. for 6 hrs. Saturated Na₂CO₃ was added and the solution was extracted with CHCl₃ twice; the combined CHCl₃ was washed with DI H₂O, dried over Mg₂SO₄, and concentrated in vacuo to give yellow oil. (0.23 g) Yield (73%). ¹H-NMR (360 MHz, CDCl₃) δ 3.91 (t, J=5.62, 4H), 2.86 (t, J=5.58, 4H), 2.50 (s br, 1H), 1.84 (t, J=5.72 Hz, 4H), 1.73 (quintet, J=3.56, 2H); ¹³C-NMR (90 MHz, CDCl₃) δ 108.62, 59.41, 43.26, 34.55, 25.87; ESI-MS: m/z [M+H⁺]⁺=158.5.

3-Aza-spiro[5.5]undecane-7,11-dithione (11)

Synthesis of 11 was accomplished using the same procedure as described for 10. Yield (78%). ¹H-NMR (360 MHz, CDCl₃) δ 2.96 (t, J=5.39, 4H), 2.83 (t, J=5.39, 4H), 2.06-1.97 (m, 6H), 1.56 (s, 1H); ¹³C-NMR (90 MHz, CDCl₃) δ 48.97, 42.49, 38.87, 26.20, 25.87; ESI-MS: m/z [M+H⁺]⁺=190.4.

Synthesis reactions for compounds 12-13 were carried out in accordance with the following scheme and description:

8-Aza-spiro[4.5]decane (12)

Synthesis of 12 was accomplished following the same procedure as described for 1. Yield (72%). ¹H-NMR (360 MHz, CDCl₃) δ 2.80 (t, J=5.62, 4H), 1.61 (t, J=5.62, 4H), 1.43-1.40 (m, 8H); ¹³C-NMR (90 MHz, CDCl₃) δ 44.18, 41.43, 38.70, 35.45, 24.46; ESI-MS: m/z [M+H⁺]⁺=140.6.

8-(4,5-Dihydro-1H-imidazol-2-yl)-8-aza-spiro[4.5]decane (13)

Synthesis of 13 was accomplished following the same procedure as described for 2. Yield (63%). ¹H-NMR (360 MHz, CDCl₃) δ 3.70 (s, 4H), 3.44 (t, J=5.65, 4H), 1.63 (t, J=5.65, 4H), 1.53-1.44 (m, 8H); ¹³C-NMR (90 MHz, CDCl₃) δ 159.44, 45.00, 43.40, 40.66, 37.59, 36.58; ESI-MS: m/z [M+H⁺]⁺=208.4.

Synthesis reactions for compounds 14-15 were carried out in accordance with the following scheme and description:

2-(octahydroisoquinolin-2(1H)-yl)-4,5-dihydro-1H-imidazol-1-ium iodide (15)

Synthesis of 15 was accomplished following the same procedure as described for 2. Yield (61%). Cis/trans mixture. ¹H-NMR (360 MHz, CDCl₃) δ 8.22 (s br, 2H), 3.74-3.59 (m, 4H), 3.29-3.24 (m, 4H), 1.73-1.30 (m, 12H); ¹³C-NMR (90 MHz, CDCl₃) δ 158.64, 158.47, 50.19, 46.93, 45.33, 42.50, 40.94, 40.05, 34.94, 32.69, 31.93, 31.55, 30.78, 28.81, 25.85, 25.52, 25.09, 23.97, 31.51; ESI-MS: m/z [M+H⁺]⁺=208.5.

Synthesis reactions for compounds 16-17 were carried out in accordance with the following scheme and description:

tricyclo[5.2.1.0 2,6]dec-8-ylaminium chloride (16)

Synthesis of 16 was performed in accordance with the same procedure as described for 8. Yield (82%). Cis/trans mixture. ¹H-NMR (360 MHz, CDCl₃) δ 3.49-3.44 (m, 1H), 2.25-2.24 (m, 1H), 2.11-2.05 (m, 3H), 2.00-1.93 (m, 3H), 1.72-1.70 (m, 1H), 1.60-1.57 (m, 1H), 1.29-1.20 (m, 2H), 1.04-0.93 (m, 3H); ¹³C-NMR (90 MHz, CDCl₃) δ 50.98, 43.69, 40.69, 38.66, 33.95, 32.07, 31.71, 31.50, 26.36; ESI-MS: m/z [M+H⁺]⁺=152.5. N-methyl-N-tricyclo[5.2.1.0 2,6]dec-8-ylaminium chloride (17)

Synthesis of 17 was performed in accordance with the same procedure as described for 3. Cis/trans mixture. ¹H-NMR (360 MHz, CDCl₃) δ 3.26-3.20 (m, 1H), 2.60 (s, 3H), 2.41-2.22 (m, 2H), 2.22-2.20 (m, 1H), 2.08-2.02 (m, 2H), 1.92-1.90 (m, 2H), 1.64-1.61 (m, 1H), 1.54-1.51 (m, 1H), 1.31-1.24 (m, 2H), 1.10-1.07 (m, 1H), 0.96-0.91 (m, 2H); ¹³C-NMR (90 MHz, CDCl₃) δ 68.43, 60.24, 47.63, 42.51, 40.72, 39.34, 33.62, 32.73, 32.58, 32.25, 26.94; ESI-MS: m/z [M+H⁺]⁺=166.5.

Example 3 SAR of BL-1743

Table 1, below, shows the results of studies that were conducted to determine the activity and IC₅₀ for the inventive compounds, as well as for amantadine and BL-1743 (compound 1). AM2 is the strain of influenza A virus on which the compounds were tested, and AM2(V27A) refers to AM2 virus that possesses the valine→alanine mutation at residue 27 in the M2 protein.

TABLE 1 AM2 AM2(V27A) Compounds % Activity Current recovery % Activity IC₅₀ (μM)

6% 30% after 70 mins 99.1% (16)

1 (25%) 2 (5%) 3 (7%) 1 (90% after 5 mins) 2 (90% after 45 mins) 3 (30% after 5 mins) 1 () 2 (0.92) 3 (20.6)

4 (30%) 5 (60%) 7 (13%) 4 (90% after 15 mins) 5 (90% after 15 mins) 7 (90% after 15 mins) 4 (NA) 5 (NA) 7 (22.8)

6 (14%) 6 (90% after 15 mins) 6 (15.3)

8 (11%) 9 (8%) 8 (8% after 5 mins) 9 (30% after 5 mins) 8 (47.34%) 9 (68.39%) 8 (1.72) 9 (15.7)

10 (100%) 11 (12%) 10 11 (60% after 5 mins) 10 (NA) 11 (37.6)

12 (16.2%) 12 (90% after 15 mins) 12 (8.14)

14 (45%) 15 (13.5%) 14 (90% after 15 mins) 14 (NA) 15 (29.5)

16 (5%) 17 (11%) 16 (43% after 5 mins) 17 (40% after 5 mins) 16 (15.3) 17 (13.6)

Initial studies involved the removal of the imidazoline head group of BL-1743 (1; 3-(4,5-Dihydro-1H-imidazol-2-yl)-3-aza-spiro[5.5]undecane); it was observed that the potency of 2 (3-Aza-spiro[5.5]undecane) greatly increases to IC₅₀=0.92 μM. That indicates the imidazoline head group may interfere the binding of M2 to BL-1743. Imidazoline head group was also replaced by carboxamide (4), carbothioamide (5), sulfonamide (6) and carboximidamide (7), all of which containing a polar H bonding donor/acceptor head group. Increases of potency were seen for 6 and 7, while no improvement of potency was observed with respect to 4 and 5. Methylation of the 1 with was found to reduce the activity to IC₅₀=20.6 μM (3).

Further improvement was made to change secondary amine to primary amine (8) and methyl amine (9), although both of failed to show improved activity, and both had slightly decreased potency. (IC₅₀ for 8, 9 are 11.72 μM, 15.7 μM respectively). Ketal (10) and dithiene (11) version of the spirene amine were also synthesized; those two compounds retain the 3D conformation of spirene amine, but have increased hyphophilicity (CLogP10=−0.298, CLogP11=1.282) comparing with 1 (CLogP1=3.38). Surprisingly, ketal substitution completely abolishes the binding affinity (IC₅₀>100 μM), while dithiene still show certain degree of activity (IC₅₀=37.6 μM). Comparison of CLogPs of different compounds revealed that active compounds all have CLogP value between 2 to 4, while more hydrpophilic compound like 10 (CLogP=−0.298) have no activity at 100 μM tested, the reason might be the inaccessibility of this compound to the channel in the membrane.

In the next step, contraction of the bottom cyclohexene ring to cyclopropane (12) was also found to be unfavorable (IC₅₀=8.14 μM). Installation of the imidazoline head group once again was shown to be detrimental to the activity (13). Efforts were also made to synthesize the 4-monosubstituted piperidine imidazoline shown below; unfortunately none of them had detectable activity at 100 μM.

It was also of interest to determine whether other fused ring systems would have better inhibitory properties. Tricyclo[5.2.1.02,6]decan (14,15) and Decahydroisoquinoline (16, 17) have been selected, and found to be not advantageous over the spirene template.

Without intending to be bound by any particular theory or theories of operation, some nonlimiting conclusions could be made based on the initial SAR study of BL-1743:

1) Imidazoline head group intereferes with the M2 binding with inhibitor;

2) Polar head groups which containing H bonding donor groups, especially amines are beneficial for activity, as N-methylation reduces potency;

3) Spirene cyclohexene rings are preferred.

4) There is a correlation between inhibitor activity and hydrophobicity cLogP, with cLogP between 2 to 4 preferred.

Example 3 Synthesis and Activity Studies of Additional Exemplary Influenza A M2 Proton Channel Inhibitors

Synthesis of compounds 18-19 were carried out in accordance with the following schemes and description:

spiro[5.5]undecane-3-carbaldehyde (intermediate A)

To a three neck, N₂ protected RBF was added (Methoxymethyl)triphenylphosphonium chloride (0.348 g, 1 mmol) and THF (10 ml). The solution was cooled down to −78° C. and LDA (1.2 mmol) was added dropwise via syringe, after addition the solution was slowly warmed to room temperature (15 mins) and kept stirring for 1 hr. The solution was again cooled down to −78° C. and spiro[5.5]undecan-3-one (0.166 g, 1 mmol) in THF was added dropwise via syringe. The reaction was left stirring overnight, and quenched cautiously with H₂O, CH₂Cl₂ was added and the solution was extracted with saturated NH₄Cl, brine, followed by drying with anhydrous MgSO₄. The solution was filtrated and dried in vacuum to give brown solid. The brown solid was washed with ether several times (3×5 ml), the ether solution was combined and dried in vacuum again until no more brown solid formed. To this brown oil was added THF (2 ml) and 5M HCl, the solution was heated to reflux for 2 hrs, cooled down to room temperature and neutralized with 1M NaHCO₃, extracted with CH₂Cl₂, and dried with anhydrous MgSO₄. The final product was purified by flash column (50% CH₂Cl₂/Hexane to 100% CH₂Cl₂) to give 0.116 g spiro[5.5]undecane-3-carbaldehyde as brown oil. (Yield: 70% for two steps). ¹H-NMR (360 MHz, CDCl₃) δ 9.63 (s, 1H), 2.22-2.18 (m, 1H), 1.82-1.21 (m, 18H); ¹³C-NMR (90 MHz, CDCl₃) δ 205.30, 50.51, 45.12, 40.10, 35.35, 33.54, 32.31, 32.87, 29.92, 27.07, 21.84, 21.69, 21.15.

spiro[5.5]undecan-3-yl(1-trityl-1H-imidazol-4-yl)methanol (intermediate B; see Turner, R. M.; Lindell, S. D.; Ley, S. V. Journal of Organic Chemistry 1991, 56, 5739-5740)

4-Iodo-1-trityl-1H-imidazole (0.436 g, 1 mmol) in THF was protected with N₂, EtMgBr in THF (1 mmol) was added dropwise and the mixture was stirred for 30 mins. Spiro[5.5]undecane-3-carbaldehyde (0198 g, 1.1 mmol) in THF was added dropwise and the mixture was stirred overnight. The reaction was quenched with saturated NH₄Cl and extracted with CH₂Cl₂. The combined CH₂Cl₂ was dried with MgSO₄ and concentrated in vacuo. Flash column purification (CHCl₃ to 5% CH₃OH/CH₃Cl) yield 0.343 g spiro[5.5]undecan-3-yl(1-trityl-1H-imidazol-4-yl)methanol as white solid (Yield: 70%). ¹H-NMR (360 MHz, CDCl₃) δ 7.41 (s, 1H), 7.36-7.33 (m, 10H), 7.17-7.13 (m, 5H), 6.81 (s, 1H), 4.40 (d, J=6.2 Hz, 1H), 1.69-1.63 (m, 4H), 1.40-1.32 (m, 10H), 1.28-1.20 (m, 4H), 1.04-1.01 (m, 1H); ¹³C-NMR (90 MHz, CDCl₃) δ 144.83, 143.78, 139.10, 130.95, 129.62, 129.44, 120.36, 76.92, 74.16, 45.58, 43.02, 37.70, 33.46, 33.22, 28.22, 25.71, 25.24, 25.02, 24.31, 22.81; ESI-MS: m/z [M+Na]⁺=513.2.

(3-Aza-spiro[5.5]undec-3-yl)-(3H-imidazol-4-yl)-methanol (19)

Spiro[5.5]undecan-3-yl(1-trityl-1H-imidazol-4-yl)methanol (0.49 g, 1 mmol) was dissolved in 3 ml 20% TFA/CH₂Cl₂, the mixture was stirred 2 hrs at room temperature. Excess TFA and CH₂Cl₂ were removed by purging N₂, the final product was subsequently purified by flash column (5% CH₃OH/CH₂Cl₂ to 10% CH₃OH/CH₂Cl₂) to yield white solid (0.203 g, Yield 82%). ¹H-NMR (360 MHz, CDCl₃) δ 8.78 (s, 1H), 7.36 (s, 1H), 4.56 (d, J=6.25 Hz, 2H), 1.70-1.61 (m, 4H), 1.42-1.36 (m, 10H), 1.29-1.19 (m, 5H), 1.04-1.03 (m, 2H); ¹³C-NMR (90 MHz, CDCl₃) δ 138.24, 134.87, 116.80, 70.59, 45.65, 42.94, 37.42, 33.41, 33.18, 28.20, 25.05, 24.10, 22.96, 22.76; ESI-MS: m/z [M+H]⁺=249.7.

3-[Fluoro-(3H-imidazol-4-yl)-methyl]-3-aza-spiro[5.5]undecane (18)

DAST (0.146 ml, 1 mmol) was added to dry CH₂Cl₂ under a N₂ atmosphere. The solution was cooled to −78° C., spiro[5.5]undecan-3-yl(1-trityl-1H-imidazol-4-yl)methanol (0.49 g, 1 mmol) in CH₂Cl₂ was added dropwise. The solution was allowed to warm to room temperature and stirred for another 2 hrs. H₂O was added and CH₂Cl₂ layer was separated. The organic layer was washed with brine, dried over MgSO₄, concentrated in vacuo and purified by flash column (2% CH₃OH/CH₂Cl₂ to 5% CH₃OH/CH₂Cl₂) to yield 0.37 g yellow solid. (Yield: 75%). The trityl protection group was subsequently removed by treatment with 20% TFA/CH₂Cl₂ as described for 19. (Yield: 81%). ¹H-NMR (360 MHz, CDCl₃) δ 8.74 (s, 1H), 7.35 (s, 1H), 4.46 (d, J=6.32 Hz, 2H), 1.70-1.61 (m, 4H), 1.42-1.36 (m, 10H), 1.29-1.19 (m, 5H), 1.04-1.03 (m, 2H); ¹³C-NMR (90 MHz, CDCl₃) δ 138.24, 134.83, 116.80, 98.4, 45.55, 42.96, 37.52, 33.44, 33.19, 28.21, 25.05, 24.10, 22.97, 22.76; ESI-MS: m/z [M+H]⁺=251.4.

Synthesis of compounds 20-21 were carried out in accordance with the following scheme and description:

3-(1H-Imidazol-4-yl)-2-(spiro[5.5]undec-3-ylamino)-propionic acid methyl ester (20)

To a solution of spiro[5.5]undecan-3-one (0.166 g, 1 mmol) and Histidine methyl ester hydrochloride (0.205 g, 1 mmol) in dicholoroethane was added NaBH(OAc)₃ (0.25 g, 1.2 mmol) and HCO₂H (72 ul, 1.2 mmol). The mixture was stirred overnight and slowly neutralized with NaHCO₃ solution. The solution was subsequently extracted with CH₂Cl₂. Combined organic layer was washed with brine, dried with MgSO₄ and concentrated in vacuo. The product was separated by flash column (5% CH₃OH/CH₂Cl₂ to 10% CH₃OH/CH₂Cl₂) (0.233 g, Yield: 75%). ¹H-NMR (360 MHz, CDCl₃) δ 7.52 (s, 1H), 6.80 (s, 1H), 3.70 (s, 3H), 3.66-3.63 (m, 1H), 3.00-2.84 (m, 2H), 2.37-2.35 (m, 1H), 1.65-1.57 (m, 4H), 1.37-1.34 (m, 9H), 1.20-1.17 (m, 3H), 1.05-1.00 (m, 2H); ¹³C-NMR (90 MHz, CDCl₃) δ 175.44, 134.78, 131.25, 121.04, 58.86, 56.32, 52.16, 50.60, 40.91, 35.19, 35.08, 32.81, 32.28, 30.19, 29.14, 28.02, 27.08, 22.04, 21.76; ESI-MS: m/z [M+H]⁺=320.7.

(5-Guanidino-2-(spiro[5.5]undec-3-ylamino)-pentanoic acid methyl ester (21)

Synthesis of 21 was accomplished using the same procedure as described for 20. (Yield: 43%). ¹H-NMR (360 MHz, CDCl₃) δ 9.34 (br s, 1H), 8.64 (br s, 1H), 7.69 (s, 1H), 6.95 (br s, 3H), 4.01-3.99 (m, 1H), 3.84 (s, 3H), 3.24-3.23 (m, 2H), 3.06-3.05 (m, 1H), 2.12-2.10 (m, 2H), 2.00-1.67 (m, 8H), 1.40-1.37 (m, 8H), 1.26-1.20 (m, 2H), 1.06-1.03 (m, 2H); ¹³C-NMR (90 MHz, CDCl₃) δ 169.00, 157.55, 70.06, 59.06, 57.01, 53.78, 49.80, 40.95, 34.70, 31.84, 31.56, 27.39, 26.86, 24.96, 24.39, 23.57, 21.91, 21.65; ESI-MS: m/z [M+H]⁺=340.3.

Synthesis of compounds 22-23 were carried out in accordance with the following scheme and description:

4,4-Dimethyl-piperidine hydrochloride (22)

Synthesis of 22 was accomplished using the same procedure as described for 2. (Yield: 82%). ¹H-NMR (360 MHz, CDCl₃) δ 9.37 (br s, 2H), 3.15 (t, J=6.0, 4H), 1.68 (t, J=6.0, 4H), 1.03 (s, 6H); ¹³C-NMR (90 MHz, CDCl₃) δ 40.64, 35.21, 28.29, 27.64; ESI-MS: m/z [M+H]⁺=114.6.

2-Aza-spiro[4.5]decane hydrochloride (23)

Synthesis of 23 was accomplished using the same procedure as described for 2. (Yield: 85%). ¹H-NMR (360 MHz, CDCl₃) δ 9.34 (br s, 2H), 3.19-3.09 (m, 4H), 1.77-1.73 (m, 2H), 1.71-1.62 (m, 2H), 1.37 (q, J=14.80 Hz, 7.35 Hz, 2H), 0.97 (s, 3H), 0.85 (t, J=7.45 Hz); ¹³C-NMR (90 MHz, CDCl₃) δ 40.37, 33.41, 33.23, 30.70, 22.88, 7.52; ESI-MS: m/z [M+H]⁺=128.2.

Compound 24,3-Aza-spiro[5.5]undecane-2,4-dione, was obtained from Bosche Scientific, LLC (New Brunswick, N.J.).

Synthesis of compounds 25-26 were carried out in accordance with the following scheme and description:

3-(3H-Imidazol-4-yl)-spiro[5.5]undecan-3-ol (25)

Synthesis of 25 was accomplished using the same procedure as described for 19. (Yield for 2 steps: 62%). ¹H-NMR (360 MHz, CDCl₃) δ 8.41 (s, 1H), 7.17 (s, 1H), 1.95-1.90 (m, 2H), 1.88-1.79 (m, 2H), 1.56-1.42 (m, 12H), 1.33-1.29 (m, 2H); ¹³C-NMR (90 MHz, CDCl₃) δ 138.62, 124.13, 119.21, 73.21, 38.24, 33.13, 33.10, 31.17, 28.14, 21.07; ESI-MS: m/z [M+H]⁺=235.6.

5-Spiro[5.5]undec-3-yl-1H-imidazole (26)

To a stirred solution of 3-(1-trityl-1H-imidazol-4-yl)spiro[5.5]undecan-3-ol (0.476 g, 1 mmol) in CH₂Cl₂ at 0° C. was added Et3SiH (0.383 ml, 2.4 mmol), followed by BF₃*OEt₂ (0.377 ml, 3 mmol). The solution was allowed to warm to room temperature and stirred for 2 hrs. The reaction was quenched with saturated NH₄Cl and extracted with CH₂Cl₂. The combined CH₂Cl₂ was dried with MgSO₄ and concentrated in vacuo. Flash column purification (CHCl₃ to 2% CH₃OH/CH₃Cl) yielded 0.37 g 4-(spiro[5.5]undecan-3-yl)-1-trityl-1H-imidazole as white solid (Yield: 80%). The trityl protection group was subsequently removed by treatment with 20% TFA/CH₂Cl₂ as described for 19. (Yield: 78%). ¹H-NMR (360 MHz, CDCl₃) δ 8.81 (s, 1H), 7.43 (s, 1H), 6.31 (s, 1H), 2.35-2.34 (m, 2H), 2.12-2.10 (m, 2H), 1.84-1.70 (m, 1H), 1.66-1.63 (m, 2H), 1.48-1.46 (m, 8H), 1.38-1.35 (m, 2H); ¹³C-NMR (90 MHz, CDCl₃) δ 136.35, 127.63, 115.40, 42.63, 38.09, 37.55, 36.24, 33.47, 32.19, 28.24, 27.91, 23.82, 22.93, 22.87; ESI-MS: m/z [M+H]⁺=219.7.

Synthesis of compound 27 was carried out in accordance with the following scheme and description:

3-(3H-Imidazol-4-ylmethyl)-3-aza-spiro[5.5]undecane (27)

Synthesis of 27 was accomplished using the same procedure as described for 20. (Yield: 74%). ¹H-NMR (360 MHz, CDCl₃) δ 7.51 (s, 2H), 4.55 (s, 2H), 3.23-3.20 (m, 4H), 1.75-1.72 (m, 4H), 1.48-1.45 (m, 10H)); ¹³C-NMR (90 MHz, CDCl₃) δ 137.35, 123.53, 52.40, 51.59, 34.64, 31.16, 27.62, 22.51; ESI-MS: m/z [M+H]⁺=234.7.

Table 2, below, shows the results of studies that were conducted to determine the activity and rate of recovery for compounds 18-27 in the AM2 strain of influenza A virus.

TABLE 2 AM2 Compounds % Activity Current recovery

18 (25%) 19 (30%) 18 (90% after 15 mins) 19 (90% after 15 mins)

20 (85%) 20 (90% after 5 mins)

21 (87%) 21 (90% after 45 mins)

22 (55%) 22 (90% after 15 mins)

23 (6%) 23 (90% after 15 mins)

24 (51%) 51 (90% after 15 mins)

25 (40%) 26 (13%) 25 (90% after 15 mins) 26 (90% after 15 mins)

27 (70%) 27 (90% after 15 mins)

Additional compounds may be prepared as follows, wherein it is preferred that R₁ and R₂ are each independently alkyl or haloalkyl: 

1. A compound having the formula (I):

wherein A is carbon or nitrogen; a₁ and a₃ are each independently (CH₂)₁₋₃, CHR₄, C(R₄)₂, CXY, C═S, C═O, or a bond; a₂ and a₄ are each independently (CH₂)₁₋₃, CHR₄, C(R₄)₂, CXY, or a bond; R₁ is hydrogen, alkyl, aryl, aralkyl, haloalkyl, amino, alkylamino, C(R₅)R₆, R₄(R₅)R₆, R₄SO₂R₆, —NHCH(acetic acid alkyl ester)R₇, or —R₄NHCH(acetic acid alkyl ester)R₇; R₂ and R₃ are each independently C₁-C₆ alkyl or haloalkyl, or, R₂ and R₃ taken together along with the carbon atom to which they are both attached form a 3- to 8-membered ring optionally substituted with up to three R₄ substituents, and R₂ and R₃ are each independently CH₂, CHR₄, S, or O; R₄ is C₁-C₆ alkyl, haloalkyl, or aryl; R₅ is O, S, ═NH, hydroxyl, halo, or amino; R₆ is hydrogen, alkyl, aryl, aralkyl, amino, alkylamino or —NHCH(R₄)(R₈); R₇ is a moiety that contains a hydrogen bond donor; R₈ is alkylamido or haloalkylamido; X and Y are each independently halo or deuterium; and, Z is hydrogen, hydroxyl, halo, C₁-C₆ alkyl, R₁ as defined above, or is absent, or, A, R₁, and Z together form a 3- to 8-membered optionally substituted ring; or a stereoisomer, partial stereoisomer, prodrug, pharmaceutically acceptable salt, hydrate, solvate, acid hydrate, or N-oxide thereof, with the proviso that if A is nitrogen, each of a₁, a₂, a₃, and a₄ are —CH₂—, R₂ and R₃ taken together along with the carbon atom to which they are both attached form unsubstituted cyclohexyl, and Z is absent, then R₁ cannot be imidazolinyl; and, if A is nitrogen, both of a₂ and a₄ are —CH₂—, R₂ and R₃ taken together along with the carbon atom to which they are both attached form unsubstituted cyclohexyl, R₁ is hydrogen, and Z is absent, then a₁ and a₃ cannot both be C═O.
 2. The compound according to claim 1 wherein each of a₁, a₂, a₃, and a₄ are —CH₂—, and R₂ and R₃ are each alkyl.
 3. The compound according to claim 2 wherein said compound is 4,4-Dimethyl-piperidine.
 4. The compound according to claim 1 wherein R₂ and R₃ taken together along with the carbon atom to which they are both attached form a 3- to 8-membered ring.
 5. The compound according to claim 4 wherein R₂ and R₃ taken together along with the carbon atom to which they are both attached form heterocyclopentyl or heterocyclohexyl.
 6. The compound according to claim 4 wherein A is nitrogen.
 7. The compound according to claim 6 wherein a₃ is a single bond.
 8. The compound according to claim 7 wherein said compound is 2-Aza-spiro[4.5]decane.
 9. The compound according to claim 6 wherein each of a₁, a₂, a₃, and a₄ are —CH₂—.
 10. The compound according to claim 9 wherein R₁ is hydrogen or alkyl.
 11. The compound according to claim 10 wherein said compound is: 3-Methyl-3-aza-spiro[5.5]undecane; 8-Aza-spiro[4.5]decane; or 3-Aza-spiro[5.5]undecane.
 12. The compound according to claim 9 wherein R₁ is aryl or aralkyl.
 13. The compound according to claim 12 wherein said compound is: 8-(4,5-Dihydro-1H-imidazol-2-yl)-8-aza-spiro[4.5]decane; 3-(3H-Imidazol-4-ylmethyl)-3-aza-spiro[5.5]undecane;
 14. The compound according to claim 9 wherein R₁ is CH(R₅)R₆.
 15. The compound according to claim 14 wherein R₆ is amino.
 16. The compound according to claim 15 wherein said compound is: 3-Aza-spiro[5.5]undecane-3-carboxylic acid amide; 3-Aza-spiro[5.5]undecane-3-carbothioic acid amide; or, 3-Aza-spiro[5.5]undecane-3-carboxamidine.
 17. The compound according to claim 2 wherein A is carbon.
 18. The compound according to claim 17 wherein each of a₁, a₂, a₃, and a₄ are —CH₂—.
 19. The compound according to claim 18 wherein A, R₁, and Z together form a 3- to 8-membered optionally substituted ring.
 20. The compound according to claim 19 wherein A, R₁, and Z together form imidazolidin-4-one, optionally substituted with up to three substituents independently selected from alkyl, halo, haloakyl, aryl, aralkyl, amino, and aminoalkyl.
 21. The compound according to claim 18 wherein R₂ and R₃ taken together along with the carbon atom to which they are both attached form heterocyclopentyl or heterocyclohexyl.
 22. The compound according to claim 18 wherein R₁ is aryl, amino, or alkylamino.
 23. The compound according to claim 22 wherein said compound is: Spiro[5.5]undec-3-ylamine; or, Methyl-spiro[5.5]undec-3-yl-amine.
 24. The compound according to claim 22 wherein Z is hydrogen or hydroxyl.
 25. The compound according to claim 24 wherein said compound is: 3-(3H-Imidazol-4-yl)-spiro[5.5]undecan-3-ol; or, 5-Spiro[5.5]undec-3-yl-1H-imidazole.
 26. The compound according to claim 18 wherein R₁ is CH(R₅)R₆.
 27. The compound according to claim 26 wherein R₅ is halo or hydroxyl.
 28. The compound according to claim 26 wherein R₆ is aryl.
 29. The compound according to claim 28 wherein said compound is: (3-Aza-spiro[5.5]undec-3-yl)-(3H-imidazol-4-yl)-methanol; or, 3-[Fluoro-(3H-imidazol-4-yl)-methyl]-3-aza-spiro[5.5]undecane.
 30. The compound according to claim 18 wherein R₁ is —NHCH(acetic acid alkyl ester)R₇.
 31. The compound according to claim 30 wherein R₇ is a side chain of an amino acid that contains an H-bond donor.
 32. The compound according to claim 31 wherein R₇ is the arginine side chain or the histidine side chain.
 33. The compound according to claim 32 wherein said compound is: 3-(1H-Imidazol-4-yl)-2-(spiro[5.5]undec-3-ylamino)-propionic acid methyl ester; or, 5-Guanidino-2-(spiro[5.5]undec-3-ylamino)-pentanoic acid methyl ester.
 34. A composition comprising a compound according to claim 1 and a pharmaceutically acceptable carrier, diluent, or excipient.
 35. A method for treating an influenza A virus-affected disease state or infection comprising the step of administering to a subject in need thereof a composition comprising a compound of formula (I):

wherein A is carbon or nitrogen; a₁ and a₃ are each independently (CH₂)₀₋₃, CHR₄, C(R₄)₂, CXY, C═O, or C═S; a₂ and a₄ are each independently (CH₂)₀₋₃, CHR₄, C(R₄)₂, or CXY; R₁ is hydrogen, alkyl, aryl, aralkyl, haloalkyl, amino, alkylamino, CH(R₅)R₆, R₄(R₅)R₆, R₄SO₂R₆, —NHCH(acetic acid alkyl ester)R₇, or —R₄NHCH(acetic acid alkyl ester)R₇; R₂ and R₃ are each independently C₁-C₆ alkyl or haloalkyl, or, R₂ and R₃ taken together along with the carbon atom to which they are both attached form a 3- to 8-membered ring optionally substituted with up to three R₄ substituents, and R₂ and R₃ are each independently CH₂, CHR₄, S, or O; R₄ is C₁-C₆ alkyl, haloalkyl, or aryl; R₅ is O, S, ═NH, hydroxyl, halo, or amino; R₆ is hydrogen, alkyl, aryl, aralkyl, amino, alkylamino, or —NHCH(R₄)(R₈); R₇ is a hydrogen bond donor; R₈ is alkylamido or haloalkylamido; X and Y are each independently halo or deuterium; and, Z is hydrogen, hydroxyl, halo, C₁-C₆ alkyl, R₁, or is absent, or, A, R₁, and Z together form a 3- to 8-membered optionally substituted ring; or a stereoisomer, partial stereoisomer, prodrug, pharmaceutically acceptable salt, hydrate, solvate, acid hydrate, or N-oxide thereof, with the proviso that if A is nitrogen, each of a₁, a₂, a₃, and a₄ are —CH₂—, R₂ and R₃ taken together along with the carbon atom to which they are both attached form unsubstituted cyclohexyl, and Z is absent, then R₁ cannot be imidazolinyl.
 36. The method according to claim 35 wherein said influenza A virus-affected disease state or infection comprises influenza (flu).
 37. The method according to claim 35 wherein said influenza A virus-affected disease state or infection comprises one or more of pneumonia, bronchitis, sinus infection, and ear infection.
 38. The method according to claim 35 said composition additionally comprises a pharmaceutically acceptable carrier, diluent, or excipient.
 39. The method according to claim 35 wherein each of a₁, a₂, a₃, and a₄ are —CH₂—, and R₂ and R₃ are each alkyl.
 40. The method according to claim 39 wherein said compound is 4,4-Dimethyl-piperidine.
 41. The method according to claim 35 wherein R₂ and R₃ taken together along with the carbon atom to which they are both attached form a 3- to 8-membered ring.
 42. The method according to claim 41 wherein R₂ and R₃ taken together along with the carbon atom to which they are both attached form heterocyclopentyl or heterocyclohexyl.
 43. The method according to claim 41 wherein A is nitrogen.
 44. The method according to claim 43 wherein a₁ and a₃ are both C═O and R₁ is hydrogen.
 45. The method according to claim 44 wherein said compound is 3-Aza-spiro[5.5]undecane-2,4-dione.
 46. The method according to claim 43 wherein a₃ is a single bond.
 47. The method according to claim 46 wherein said compound is 2-Aza-spiro[4.5]decane.
 48. The method according to claim 43 wherein each of a₁, a₂, a₃, and a₄ are —CH₂—.
 49. The method according to claim 48 wherein R₁ is hydrogen or alkyl.
 50. The method according to claim 49 wherein said compound is: 3-Methyl-3-aza-spiro[5.5]undecane; 8-Aza-spiro[4.5]decane; or, 3-Aza-spiro[5.5]undecane.
 51. The method according to claim 48 wherein R₁ is aryl or aralkyl.
 52. The method according to claim 51 wherein said compound is: 8-(4,5-Dihydro-1H-imidazol-2-yl)-8-aza-spiro[4.5]decane; or, 3-(3H-Imidazol-4-ylmethyl)-3-aza-spiro[5.5]undecane;
 53. The method according to claim 48 wherein R₁ is CH(R₅)R₆.
 54. The method according to claim 53 wherein R₆ is amino.
 55. The method according to claim 54 wherein said compound is: 3-Aza-spiro[5.5]undecane-3-carboxylic acid amide; 3-Aza-spiro[5.5]undecane-3-carbothioic acid amide; or, 3-Aza-spiro[5.5]undecane-3-carboxamidine.
 56. The method according to claim 41 wherein A is carbon.
 57. The method according to claim 56 wherein each of a₁, a₂, a₃, and a₄ are —CH₂—.
 58. The method according to claim 57 wherein A, R₁, and Z together form a 3- to 8-membered optionally substituted ring.
 59. The method according to claim 58 wherein A, R₁, and Z together form imidazolidin-4-one, optionally substituted with up to three substituents independently selected from alkyl, halo, haloakyl, aryl, aralkyl, amino, and aminoalkyl.
 60. The method according to claim 57 wherein R₂ and R₃ taken together along with the carbon atom to which they are both attached form heterocyclopentyl or heterocyclohexyl.
 61. The method according to claim 57 wherein R₁ is aryl, amino, or alkylamino.
 62. The method according to claim 61 wherein said compound is: Spiro[5.5]undec-3-ylamine; or, Methyl-spiro[5.5]undec-3-yl-amine.
 63. The method according to claim 61 wherein Z is hydrogen or hydroxyl.
 64. The method according to claim 63 wherein said compound is: 3-(3H-Imidazol-4-yl)-spiro[5.5]undecan-3-ol; or, 5-Spiro[5.5]undec-3-yl-1H-imidazole.
 65. The method according to claim 57 wherein R₁ is CH(R₅)R₆.
 66. The method according to claim 65 wherein R₅ is halo or hydroxyl.
 67. The method according to claim 65 wherein R₆ is aryl.
 68. The method according to claim 67 wherein said compound is: (3-Aza-spiro[5.5]undec-3-yl)-(3H-imidazol-4-yl)-methanol; or, 3-[Fluoro-(3H-imidazol-4-yl)-methyl]-3-aza-spiro[5.5]undecane.
 69. The method according to claim 57 wherein R₁ is —NHCH(acetic acid alkyl ester)R₇.
 70. The method according to claim 69 wherein R₇ is a side chain of an amino acid that contains an H-bond donor.
 71. The method according to claim 70 wherein R₇ is the arginine side chain or the histidine side chain.
 72. The method according to claim 71 wherein said compound is: 3-(1H-Imidazol-4-yl)-2-(spiro[5.5]undec-3-ylamino)-propionic acid methyl ester; or, 5-Guanidino-2-(spiro[5.5]undec-3-ylamino)-pentanoic acid methyl ester. 